martin



May 22, 1928;

T. G. MARTIN AUTOMATIC TELEPHONE SYSTEM Original Filed May 10, 1923 2 Sheet-Sheet Imrsn 2r Talb'c'wTE. F l' ar" m 4G. it k bu W May 22, 1928. Re. 16,975

v T. G. MARTIN AUTOMATIC TELEPHONE SYSTEM Reissued May 22, 1928.

T'ES' [UNITED STA Re.16',975 PATENT OFFICE.

TALBOT G. MARTIN, OF CHICAGO, ILLINOIS, ASSIGNOR, IBY MESNE ASSIGNMENTS, TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WARE;

AUTOMATIC TELEPHONE SYSTEM.

Original N L" 1,564,4s7, dated December a, 1925, Serial No. 631,931, filed ma 10, 1923. Application re:

reissue filed June 11, 1926. Serial: No. 115,352.

ahead after each vcall and is. employed to even up the traific on the various finder switches and also to enable a call ngsubscriber to get service eventually even though the starting loop does happen to be open at one or more'poin'ts or in case one or more finders are out of order.

Anotherobject of the invention is the production of a new and improved finder switchhaving multiple wipers for increasing its capacity.

Another object is the production of suit able circuit arrangements whereby a discriminating tone source is associated with a subscribers line at the exchange only when the line is in use. I

y The .other objects are concerned mainly with various circuit details and refinements and will be explained fully'hereinafter.

Referring now to the drawings comprising Figs. 1 and ithey show by means of the usual circuit diagrams a suificient amount of apparatus in a system embodyingthe principles of the invention to enable the i i 1IlVGIltl0l1tO be thoroughly understood and, 40

in order to be comprehended best, should be placed one above the other. i

Figure 1 shows the substations Aand A, of whichthe respective lines terminate at theexchange in the banks of finder switches,

and with which are associated the line circuits LC andLC, respectively. 1 shows also the finder Fwhich has accessto the lines of substations A and A, and which is assumed to be associated with a first selector switch through the medium of the three conductors extending to the righthand edge of the drawing.

wFigurc 2 shows the common start wire distributer D, and also the finder F whose banks are mult-ipledwith the banks ofthe finderF.

The finders such as F and F are automatic switches of the well-known vertical and rotary type in which the bank contacts are arranged in horizontal rows or levels. Each of these switches has two separate sets of bank contacts and two separate sets of cooperating wipers, in order to double the normal capacity of 100 lines. Each finder also has a vertical test wiper and bank, as shown by Smith and Campbell in Automatic Telephony, second edition, Figs. 65 and 66, pages 68 and 69. The line circuit LC comprises av two-magnet two-step combination line and cut-oft relay whose magnets are indicated by the reference characters 16and 17. This relay is of the same type as the one disclosed in the co-pending application of Erickson, filed June 17, 1921, Serial No. 478,377, i. e., ithas one armature which is operated in two distinct steps, each step controlling a plurality of armature-springs hereinafter referred to as such, or merely as armatures according to standard practice. The line circuit LC is identical with the line circuit LC. 1 t Y i j The distributer D is mechanicallya simple switch having a wiper 176 which is operated in aforward direction only by the associated stepping magnet 174, as will be explained hereinafter. v

In order to explain the detailed operation of the equipment shown, it will be assumed that the subscriber at substation A desires to make-a call and, accordingly, removes his receiver fromthe switchhook. 1

When the receiver is removed at substation A, the first step coil 16 in the line circuit LC isenergized over conductors 1L and 12, being connected to conductor 11 through armature 18 and its resting contact, and conductor 12 being grounded through theresting contact of armature 22 and said armature and the common conductor 29, which is grounded through the normally closed contacts controlled by armature 193, F 2. The first step coil 16, upon becoming energized over this circuit, magnetizes the associated. core with the result that its armature, as explained in the above mentioned application, is operated only about halfway andjthe first step armature springs point has been previously shunted by the vertical off normal contacts 111. Stepping relay 1.03, upon deenergizing, opens the circuit of the rotary magnet 107 at armature are not rotated any further, and the finder its iii-matures switches through at this point. Assuming that the contacts in which .thecallin-g line terminates are in some set other than the first set in the second level, test wipers 154 and 157 engage grounded contacts and, as

a result, switching. relays 105 and 104 arev both short circuited and both windings of the shunt field relay 103are energized with the result that said relay 103 again attracts This results in locking circuits being closed for the two windings of relay 103 at contacts 132 and 133, and also in a circuit for rotary magnet 107 being closed at contacts 134. The said rotary magnet 107 again energizes with the re; sult thatthe switch wipers are stepped into engagement with the second set of bank contacts, and stepping relay 103 is again deenergized at the end of the "stroke of the rotary magnet 107. i

This alternate operation of stepping relay 103 and rotary magnet 107 continues as described until the test wiper 154 engages the ungrounded test contact 27. Vhen this occurs, switching relay 104, being no longer short circuited, energizes in series with the right hand winding of stepping relay 103. The shunt field stepping relay 103 is not again energized when the calling set" of contacts are reached notwithstanding the fact that a circuit for its left hand winding is closed through wiper 157 and the grounded test contact 34, owing to the fact that the non-energized right hand core serves as a short circuit for the magnetic flux generated in theenergized left hand core of the relay. It is true that a small amount of flux is generated in the right hand winding of relay 103, but this flux is not sufiicient to operate the armature of the relay owing to the fact that the current through the right hand winding of the relay 103 is limited by the high resistance winding of switching relay 104, through which the circuit of the right hand windingot' relay 103 now extends as follows: from the grounded release trunk conductor by way of contacts 142,

switching relay 104, right hand winding of stepping relay 103, off normal contacts 111,

y and contacts 110, 109, and 114 to battery.

Upon. energizing, switching relay 104disconnects switching relay 105 at contacts 137 opens another point the circuit of release magnet and closes a circuit for the meter M through contacts 146 at armature 139; and at armature 138 opens the circuit of the slow acting line relay 106 and T prepares to extend the start conductor 181 to the next finder. As a further result of the energization of relay 104, it disconnects the test wiper 154 from the junction of switching relay 104 and the right hand-- winding of stepping relay 103 at armature 136 and connects it to the grounded release trunk conductor 160, thereby placing ground 7 on. the test conductor 24 through the test contact 27. lVhen this occurs, the second step or cut off coil of the line circuit relay becomes energized with the result that the remaining armatures of this relay are operated. Armatures 18 and 22, upon being attracted, remove the normal battery and ground connections from the calling line, and armature 21 removes ground from start conductor 30, whereupon the group relay 171 deenergizes.

Relay 171,. upon deenergizing, in addition to removing ground from the common conductor 31 and replacing ground on the group test conductor 32 atarmature 173, opens the circuit of stepping magnet 174 at armature 172,. whereupon stepping magnet 174 deenergizes and removes ground from wiper '17 6, at the same timeadvancing the wiger 176 into engagement with start conductor182 extending to the second finder. It will now be seen that when the next call comes in, the second finder is employed even though the firstfinder F does happen to become idle in the meantime.

In the finder F, as a further result of the energization of switching relay 104, the line wipers 153 and 155 are connected up to conductors 159 and 161 at armatures 135 and 139, respectively. As aresult, the numerical switch connected with the finder F by the conductors 159 161, inclusive, is prepared for operation in the usual manner and, accordingly, places ground on release trunk conductor 160. Thisis done, it will be understood, before the slow-acting line relay 106 of the finder F has had time to deener gize. v p 3 After an interval line relay 106 deenergizes; removes ground from conductor 160 at armature 145, leaving conductor 160 grounded the associated switch as exabove described.

;After calling subscriber has coni- 139 and. its resting contact, armature 1445 and its-resting contact, contacts 147, oif-nor in'al contacts'113, and release magnet 115 to battery, Upon energizing, releasemagnet 11'5 disconnects battery from the interrupter contacts 109 110 of the rotary and Vertical' and 108,srespctively, at contacts 114, so as to prevent relay-s: 1101, and 102 from becoming, energized over Wiper 149 during the ie'lease of the connection. As a further resultof the energization of release magnet- ,115, the shaft and Wipers 'oi the finder F' restored to normal position in the usual manner, and the circuit release nlagnet lld is openednt oiii-norii al' contacts 113 by" the switch S1 aft when the latter reaches its nor-ma position. i w I I ,Assuiningth' t" the subscriber subsidtion A Iii alt'es a can, and assuming further that he does so at-Ja tiine when the distributer switch D isiii the position shown thedrawing and that the finder F i'sidi'e, the finder F iso'p'e'rat'edin the here'inbefore dc scriberl' manner, with the result that the Wipers 153-158,-in'cli1'sii' e, ar'ebrought into engagement with the contacts in Which the lines of substat ons and A terminate. In this ease, since the substation A' is not the llin substation, testlfcontact 27 is grounded and switching elay 104 of the finder-Q E accordingly.remains short circuit'ed, However, since the call is being madefrointhe substation A, test contact istheonc ivlpich'i ung -onnded and, accordingly, switching relay is no' longer shortciicu'ited' when test, wiper 157 arrives upon the said contact 34; That being the case,

switching relay 105 energizes in series with the left-li'and winding of the shunt field reliaiy Upon energizing, switching relay 105 perf j at minim-@5143 and lf li the saline operations as were performed at'iiriuas :138 Bind 13-9 'byfswi tching relay 104; ts sit'itching relay 104 at contacts 142";1and' at ati1'iatur'e'141 disconnects test it'ipei" 157 from the junction of its own winding'andlthe left-hand winding of shut field relay 103iand'coiniects it toth'e'ground edreleas trunk conductor 160, thereby ener-. gizi ng the cutoff Winding of the two-step relayof"t'lielinecircuit LC. 0

As furtherrresult of the energization of switching relay 10.5, it connects i115 theliiie fritters .156 and 1 718 %v contacts 140 and to the i sults lie c 'eiimeiore described.

. It may be stated that in case the lines of substation A and A are calling siii'iult-rincously, switching relays 10-1 and 105 both atteiiipt to one qiie ii'hen the finder has found v the "calling lines. This does not cause anj" trouble, however, because each opensthe circuit of the other-and they cannot both pun up. lli 'hoth buzztoi" n inst ant, but due-to the tact that they I 'uno't both have absolutely the smile adji'lsuncnt. one rel iij'illj iall'vo'utoi step and permit the otli to p ll in). v The line hi'cli' isn'ot connected with thistiine is found by another finderai'ter the starting ciifcuithas tended to such/finder; 4 d

,It my soi ne tinies occurthat a subscrii' er Vivi ll reiiioi e his receiver to make a ck-ill, but will climate-e his mind end replace the n, ceiver on the hoolnatter a finderhus r-itzu'ted' been exin search 01", the line and before the li'n'e v Assuming that the; finder has been found. I v F is operatingiii search'of it calling line, and ajssuinln that the ailing subscriber replaces his receiver hefoi the level in which his line 'terniinates lias bfee n reached, there 149 is engagement with a grounded. contact, circuit is closed for release magnet 115' through. oif-norinalcontacts 113, upon the closure of the tenth le'i elsh'aft springs 118. hen thisoccursdi'elease inagnet 1.15 energi es; locks itself to the grounded release trunk conductor- 160 at contacts 116; and at"contac ts114 removes battery from the"int'errupter contacts 109 and 110 so to'st'o'p the'oper'ati'onof ifertical malf ir-t 10S by opening the circuit of relity 1'01" and per- Ini tting it to deenergize, The switch does not start to rotate at this tiinefor' thev reason "that the circ'i'iit' of 'st'eppiiig relay 103' i s opened at cont-actsllif "The switch shaft and 'wipersare new restored to normal a e ti'on, and the circuit of release 1nagnet'115 isop'enetl in the usual'nianncr at Orr-110111131 contacts'll'il; whereupon said release magnet deenergiz'es; opens its contacts 116; and closes its co-n tacts'lli', Wheieupon it is able to iinn'iediatelystart in sear'ch of another c alling line in c'ase'the stii-rt conductor extending to it "is at' this time grounded due iri cith iline ealiing.

. Snider-arrangement- 1's provided. for

inductors 159 and 161, with the re;

releasing the finder F while its start wire is still grounded and in case it fails to find a calling line whilerotating." In such case the rotary movement continues until the eleventh rotary step has been taken, at which time the wipers ,153158, inclusive, willhave assed one step beyond the last set of bani; contacts, and the eleventh rotary step springs 117 are closed, with the resultthat circuit is completed for release magnet 115 from the grounded release trunk to inform conductor 160, as a result of which the re: lease magnet 115 energizes and restores the finder to normal. 1 y

In case all the finders are busy except one, and assuming the idle finder is the finder F', the circuit for the slow to energize chain relay 191 completed at all points except at oil-normal contacts 112 and, accordingly, as soon as the finder F starts to operate in its vertical movement upon the.

next call being made, the circuit of chain relay 191 is completed at off-normal contacts 112, and relay 191] energizes; closes a circuit for themeter M at contacts 192 soas to register this condition; and at armature 193 places ground through the left-hand winding of the busy tone transformer on the common conductor. 29 and removes'di rect ground therefrom. This is done so as to give a. busy tone to a calling subscriber him that no finder is at present available. The relay 191 is made. slow to pull up so as to delay the placing of the busy tone on the common conductor 29 until after the finder F calling line. 'Otherwise, the calling sub-- scriber Iniglt get a. busy signal and'hang up evenythough the finder F is searching for his line. This busy signal, of course, is

meant only for those who take off their receivers at a time when all the finders are actually, busy. m

Referring now to Fig. 1, the soralleddiscriminating tone arrangements provided for in connection with the lines ofSubstations A and A will be explained briefly. The buzzer-11 is constantly operating and induces a tone through the medium of the associated transformer on the common tone jconductor 12C j-Considering the line otsubstation A.

this tone passes and the jumper through the condenser 13. 14 to the normally open contacts 20 of the line circuit LC; These contacts are closed only when the second step coil 17 is energized and, consequently, when the line of substation A is in actual use, the tone from the buzzer ll isplaced .on the private normal conductor '14 through the contactsQOQand when; a call is extended to a toll recording operator .who has. means for associating her headset with the release trunk conductor, this tone is heard andindicates the class to which the line of the SHb Q- iP-RA ba wlg F r a fu ler descripexchange.

has had time to find the ot' the drawings inthe Ray case shows how any one of a plura-lity'of characteristictones may be placed on the private ductor 1d of the line switch C. The tone lead, however, is normally connected to the private normal conductorand a path is normally provided to battery through the relay 1 1'and stepping magnet 16. is normally load on the tone producing machine which is very undesirable in a large I It is obvious that' since the discriminating tone lead is normally disconnected from the private normal conductor inthe present case, a considerable saving in current is effected on account of the fact that the discriminating tone current is no rmal conthrown out on the private normal co-nk ductor of a line only when that line is in use. I

"There is another and possibly more serious objection to a. system in which'the discriminating tone is normally "connected.

It is common practice to provide some lines with tone, and to leave some lines without tone, depending upon the respective classes to which the lines belong. When this is done, it has been found often that the elecstrong enough to mislead the operator,

thereby defeating the purpose of the dis criminating tone arrangement. It was found that this electrostatic induction is efi'ected principally by the private normal conductors of idle lines, and thatjno appreciable interferenceiscaused by the tone on a private normal conductor when the said conductor is in use, on account of the factthati-tis then grounded. I

It was toundalso that the tone placed on idle private normal conductors caused a corresponding tone to appear on adjacent line conductors by electrostatic ln'duction. This,

also, is practically eliminated when the-pri-v vatenormal conductors are grounded. In the present case, the electrostaticinduct-ion 1s, therefore, not present .to any appreciable extent for the reasonthat the discriminating tone, is disconnected troma rivat-enormal conductor when the assoc1ate line is not in useand 1sfconnected to that conductor onl when the associated line is in use, at whic tlme jthe private normal. conductor, is

grounded, thereby preventing the electro ome inducti n r m time p a e i this.

t me. i

' It isiobvious, in any case, that With a pri- Mate normal conductor grounde dy. due to applicant has devised a very-ei ficient finder system and one embraci g a comparatively large number of calling lines and ohewhich has very reliable means for extending the start circuit, which means comprises the usual chain circuit extending through the finders and, in addition, the distributer switch D which shifts the point of access to the starting circuit after each call. It will be seen also that there is a considerable economy e ec ed, in t o 'snmp ip of i -j crimina'ting tone current, and thatj the] sou ce of cros es among t e Pr v te normal conductors is removed as concerns an Y practical results. I

llVhat is .claime dis: 1. In atelephone system,ag1-oup of l nes, group .of vfinder sw1tchesf0r extending sai lines whencalling, v

- cuit extending through all said finders in seri s, a line relay n a h nd r dir y controlled over said starting circuit, con- (acts on each relay for cxten'ding said circuit to the ndextl'finder, a start wire cornrnonto said lines, and a -distrib uter' switch intervening between said startwire said l op c r uit by means of h h. th co mon start wire can be associated withsaid loop circuit at a plurality of difierent points.

In a "telephone system, a group of lines, a 'roup of finder switches fO T extending sairf lines when calling, :a loop starting c u x ending th ugh a sai finde s inlseries, line and "switching relays in each finder, serially related contacts on the said relays in each finder controlling the continuity of said starting circuit, a start wire common to said lines, a start wire individual to each finder switch connected to said .loop

i circuit, and a distributer switch for ajsso Ci i th c x m sta t wire with any one of sa ig individual start wires. .fi -"lnia teleph n y t a g oup of li'nesfla. n n if nd r Switc e for extending ,spifiines, h n ca ling a, loop tartin 9 mm? exten ing thro gh a l s id finders in s ies, i sta m e emiacn to .s l nes,

. star re ndividual W ch finde witch c nne ted to idlQ P' ircuit, dist lt r snitch entqlled nver said me sea wireresponsi've'to successive ca' 1s, said dis- 7 st r ing irtrihuter switch having .a stepping magnet,

i'ng said lines when'calling; aloop starting circuit extending'through all said finders in series, a start wirecommon to said lines, a plurality of start wires connected to said loop circuitat difi'er'ent pointsg a distributer switch for associating said common start wire with any start wire of said plurality, means for advancing said distributer switch once for each call, and means for preventing such advance in case a succeed'ing call is made before the preceding call is located. 5. In a telephone system, a group of lines, a group of finder switches-for extending said lines when calling; a loop startingcircuit extending through all said finders'in' series, a start wire 'commonfito said Iines,a pluralitycf Ot henstart wires gQllnected to said loop circuitat different points, a distributor switch controlled over Cally advancing saiddistributer switchto preselect "another of said @ther start wires when the calling line is found. j 7

46. In a. telephone I system, a group of lines agroliip of finder switches for'extend ing fsaid lines when calling, a startcircuit ex tending through said finders serially over which the said finders may bestartedone aftergthe other in response tosuccessive calls 'a' start, wire common tosaid'lin'es automatic switching j'means responsive to'a call for changing the relat-ionbetween the common start'wire and the said start circuit to insure the starting of a difi'erent finder for the I 1 e X t c'a l'l, and-means preventing said switching means from responding to'ca'lls whichjare initiated while one or, more other calls areawaiting the action of'findejrs.

..In a telephone system, 'a'plurality of a finder {switch for extending said ines iwheri call'ing, testing means in switch for'l'ocating a calling line, said testin? I lie ifng means comprising two test wipers and a'comm on test relay with circuit connec- .t ons for testing two of sa d llnes slmultaneously, an armature on said test relay indicative of the character of the calling line, and contacts on said relay closed when the same is energized for connecting the said 1n:.ichine with said release trunk conductor.

9., In a telephone system, a plurality of groups of lines, a finder switch for extending raid lines when calling, each of said groiuas of lines being divided into two subgroups, said switch having a primary move ment to select a group and a secondary movement to select two calling lines in the selected group, two sets oi wipers in said switch corresponding to the two sub-groups,

resoectively, a secondary test wiper in each set of wipers, a primary test wiper, a double wound stepping relay, meansfor operating both windings of said stepping relay in multiple under control of said primary test wiper to drive the finder into association with the calling group, and a relay controlled overthe primary test wiper to connect thetwo windings of the stepping relay with the secondary test wipers, respectively, and to connect the impulse generating contacts with the secondaryoperating magnet, whereby thewipers are driven into engagement with the calling line.

10. In a telephone system, telephone lines of different character, a local conductor for each line, a tone source for certain of said lines, and means actuated by the closure of one of said certain calling lines for connecting its local conductor to said source.

11. In a telephone system, telephone lines of diflerent character, a local conductor for each line, a tone source for certain of said lines, and means actuated by the closure of one of said certain calling lines for connecting its local conductor to said source and for disconnecting the same therefrom upon the opening of the calling line circuit.

12. In a telephone system, telephone lines of difl'erent character, a local conductor for each line, a tone source for certain. of said lines, means actuated by the closure of one of said certain calling lines for connecting its local conductor to said source and for disconnecting the same therefrom upon the opening of the calling line circuit, an operators position, means for extending calling lines to said position, and means at said position responsive to said tone current.

13. In a telephone system, telephone lines of different character, a local conductor for each line, a tone source for certain of said lines, means actuated by the closure of one of said certain calling lines for connecting its local conductor to said source, an operators trunk, means for automatically extending said calling line to said operators trunk, and inductive means for transferring-said tone source from said local conductor to the talking conductors of said operators trunk.

14-. In a telephone system, telephone lines of diti'erent character, a local conductor for each. line, a tone source for certain of said lines, means actuated by the closure of one of said certain calling lines for connecting its local conductor to said tone source, an operato-rs trunk, means. for automatically extending said calling line to said I operators trunk, a signal therein, means for operating said signal upon said seizure of i said trunk, inductive means for transferring said tone-source from said local conductor to the talking conductors of said operators trunk, an operators telephone, and a key for connecting said trunk to said telephone. Signed by me at Chicago, Cook County, Illinois, this 2d day of June, 1926.

TALBOT. e. MARTIN. 

